METHODS OF OBSERVING BACTERIA. 103 will appear. Ix>ffler has fortunately worked out the amounts required for some of the species, and of the more important ones the following amounts of Solutions B and C must be added to 16 c.cm. of Solution A to attain the desired effect: Cholera spirillum, jú-i drop of Solution C ; Typhoid fever, I c.cm. of Solution B ; Bacillus subtilis, 28-30 drops of Solution B ; Bacillus of malignant edema, 36-37 drops of Solution B. Part of the success of the staining depends upon having the bacteria thinly spread upon the glass, and as free from albuminous and gelatinous materials as possi- ble. The cover-glass must be cleaned most painstakingly : too much heating in fixing must be avoided. After using and washing off the mordant, the preparation should be dried before the application of the anilin-water-fuchsiu solution. Pitfield1 has devised a simple and good method of staining flagella. A single solution at once mordant and stain is employed. It is made in two parts, which are filtered and mixed. A. Saturated aqueous solution of alum, 10 c.cm.; Saturated alcoholic solution of gentian-violet, i c.cm, B. Tannic acid, i gr.; Distilled water, 10 c.cm. The solutions should be made with cold water, and immediately after mixing the stain is ready for use. The cover-slip is carefully cleaned, the grease being burned off in a flame. After it has cooled the bacteria are spread upon it, well diluted with water. After drying thoroughly in the air, the stain is gradually poured on and by gentle heating brought almost to a boil; the slip 1 Med. News, Sept. 7, 1895.